This invention relates generally to an electrostatographic printer and copier, and more particularly, concerns a cleaning apparatus for removal of residual particles and agglomerates from an imaging surface.
The common additives used in color toners are zinc stearate (ZnSt), titanium dioxide (TiO2), and silica (SiO2). These are added to the toners as flow aids and charge control agents. The development process develops the toner and these additives onto the photoreceptor. When the ZnSt is deposited by the developer, it forms a uniform film covering the photoreceptor; for this reason the ZnSt film is referred to as a filming type additive. The TiO2 and SiO2 are very small particulate type additives, and are found on the photoreceptor as particles in lower concentrations compared to ZnSt. The particulate nature of TiO2 and SiO2 makes them usually easy to clean off the photoreceptor with most types of cleaners. The level of these additives on the photoreceptor depends on the development system and the concentration of additive in the toner. When the additive levels in the toner are increased, the level of additive filming on the photoreceptor also increases. At the higher additive levels we have found a very thick additive film on the photoreceptor that consists of two layers. The first layer on the photoreceptor is a thin, uniform ZnSt film. The second layer on top of the ZnSt film is a soft, thick film of ZnSt, TiO2, and SiO2. This soft, thick film is referred to as a "toner additive film".
The thickness, the surface texture, and the levels of additives in these two layers on the photoreceptor are determined using XPS (X-ray photoelectron spectroscopy) and SEM (scanning electron microscope). The thickness of the ZnSt film (i.e. the first layer on the photoreceptor) is usually less than 50 .ANG.. This is a soft smooth film that gives the photoreceptor a shiny appearance. When the thickness of this film is less than 50 .ANG., there is no adverse effect on copy quality. The "toner additive film" (i.e. the second layer) varies in thickness from about 50 .ANG. to one micron, and is a soft, discontinuous film that varies in thickness giving the surface a rough texture. When the thickness of this film starts to increase the background on the copy also starts to increase. Therefore, a method of removing or controlling the thickness of this "toner additive film" is needed.
The following disclosures may be relevant to various aspects of the present invention and may be briefly summarized as follows:
U.S. Pat. No. 4,007,982 to Stange discloses a cleaning apparatus, electrostatographic machine and process are provided wherein particulate material is removed from the surface of an electrostatographic imaging member by at least one blade member having an edge engaging the surface. The blade edge is vibrated at a frequency sufficiently high to substantially reduce the frictional resistance between the blade edge and imaging surface. The amplitude of the vibrations is controlled to a level which will insure sufficient conformity between the blade edge and the imaging surface so that adequate cleaning can be provided. Preferably the vibrations are carried out at ultrasonic frequencies with an amplitude less than about 0.005 inches.
U.S. Pat. No. 4,111,546 to Maret discloses an electrostatographic reproducing apparatus and process including a system for ultrasonically cleaning residual material from the imaging surface. Ultrasonic vibratory energy is applied to the air space adjacent the imaging surface to excite the air molecules for dislodging the residual material from the imaging surface. Preferably pneumatic cleaning is employed simultaneously with the ultrasonic cleaning. Alternatively a conventional mechanical cleaning system is augmented by localized vibration of the imaging surface at the cleaning station which are provided from behind the imaging surface.
U.S. Pat. No. 4,121,947 to Hemphill discloses a charged residual toner removed by simultaneously (1) exposing the photoconductive layer of the photoreceptor to light, (2) charging the photoconductive layer to the same polarity as that of the toner, (3) vibrating the photoreceptor to dislodge the toner by entraining the photoreceptor to dislodge the toner by entraining the photoreceptor about a roller while rotating the roller about an eccentric axis, and subjecting the toner to a force (e.g. vacuum or gravity) which draws the toner away from the photoreceptor.
U.S. Pat. No. 5,030,999 to Lindblad et al. discloses a piezoelectric transducer (PZT) device operating at a relatively high frequency coupled to the backside of a somewhat flexible imaging surface to cause localized vibration at a predetermined amplitude, and is positioned in close association with the imaging surface cleaning function, whereby residual toner and debris (hereinafter referred to as simply toner) is fluidized for enhanced electrostatic discharge of the toner and/or imaging surface and released from the mechanical forces adhering the toner to the imaging surface.
U.S. Pat. No. 5,339,149 to Lindblad et al. discloses a cleaning apparatus having a spots cleaning blade to remove residual agglomerations of particles from the imaging surface. The spots cleaning blade is made from a material that has a low coefficient of friction, low resilience and higher hardness than a standard spots blade. These properties enable the spots cleaning blade to provide a continuous slidable contact with the imaging surface to remove residual particles therefrom.
U.S. Pat. No. 5,349,428 to Derrick discloses a thin scraper blade member arranged in interference with, and at a low angle of attack with respect to the photoreceptor so that a maximum shearing force can be applied by the blade to the spot-causing agglomerate particles for removal thereof. A slit extends laterally from one side of the blade and parallel to the edge of the blade, so that blade tuck occurrence is minimized. The slits serve to reduce the load and eliminate forces on the ends of the blade that cause the blade to tuck under. The slit also improves the range of tolerance of interference of the blade surface with respect to the photoreceptor surface before blade tuck occurs. A relatively low load is applied to the blade, so that the problems associated with the frictional sealing contact that must occur in the normal cleaning engagement of blades with a charge retentive surface are avoided.
U.S. Pat. No. 5,416,572 to Kolb et al. discloses an agglomerate spot cleaning blade supported to a cleaning housing, thereby forming a substantially enclosed chamber, in sealing engagement with respect to the photoreceptor surface. Contact is maintained between a cleaning brush, located within a cleaning housing, and a blade, whereby rotating brush fibers remove accumulated agglomerate debris particles from the blade. A substantially air-flow free environment is maintained for removal of residual toner and debris from the photoreceptor surface and the blade, without the need for a separate vacuum/air removal system assist, or a separate manual maintenance step.